THE LAUSANNE CONGRESS

The International Society for Photogrammetry held the Xlth International Congress at Lausanne during July 1968. The authors review the activities of five of the seven I.S.P. Commissions.     

A Pull-Up Shallow Water Seismometer

An inexpensive Pull-Up Shallow Water Seismometer (PUSS) has been designed and built to conduct long range seismic refraction experiments in the North Sea and the continental shelf around Britain, with the particular goal of studying the crustal and lithospheric structure under the epeirogenic basin of the North Sea. Signals from a gimbal-mounted 3-component geophone and a hydrophone are frequency modulated and mixed with clock and flutter correction signals before being recorded on a standard speed cassette tape recorder, with one hour of recording time. A 100 hour programmable timer allows the interval between the time of reset of the clock and each shot window of optional 5 or 10 min duration, to be preselected. The PUSS is launched and recovered using a pull-up technique originally developed for current meters. The replay system is also described.In May 1976 sea trials of 5 PUSSes were conducted along a 200 km refraction line in the North Sea. The encouraging performance of the equipment resulted in the decision to build a further 10 units and to proceed with a 400 km refraction line planned for the summer of 1977.     

Seasonally Hypersaline Estuaries in Mediterranean-climate Regions

Data collected in three Californian estuaries indicate that hypersaline conditions exist during the dry summers typical of a Mediterranean climate. The generalised seasonal and longitudinal hydrographic structures are described and explained. It is argued that this seasonal hypersalinity is common and that it represents a major class of estuaries. The observed accumulation of salt indicates surprisingly long residence times in small basins which have free exchange with the ocean. This semi-isolation of the inner basin leads to a large build-up or severe depletion of nutrients, pollutants and plankton in these systems. Of concern are the trends to increase pollutant loading in the same systems that are experiencing an increase in residence times owing to freshwater extraction in the watershed.     

Wavelet analysis of bathymetric sidescan sonar data for the classification of seafloor sediments in Hopvågen Bay - Norway

In this paper we examine the use of bathymetric sidescan sonar for automatic classification of seabed sediments. Bathymetric sidescan sonar, here implemented through a small receiver array, retains the advantage of sidescan in speed through illuminating large swaths, but also enables the data gathered to be located spatially. The spatial location allows the image intensity to be corrected for depth and insonification angle, thus improving the use of the sonar for identifying changes in seafloor sediment. In this paper we investigate automatic tools for seabed recognition, using wavelets to analyse the image of Hopvågen Bay in Norway. We use the back-propagation elimination algorithm to determine the most significant wavelet features for discrimination. We show that the features selected present good agreement with the grab sample results in the survey under study and can be used in a classifier to discriminate between different seabed sediments.     

The environmental management of shipping

The environmental management of shipping requires systematic consideration of the geography of shipping routes, ship types and cargoes, and environments which can form the basis of a classificatory approach to Environmental Impact Assessment (EIA). Beyond this, effective environmental management depends in the first instance upon sound information management including monitoring of the environment, surveillance of shipping and information technology, followed by information assessment including, in particular, risk and environmental impact. The general management dimension includes co-ordination of technical management and organisational aspects related to shipping. It is suggested that effective environmental management of shipping may depend upon a regionalisation of the marine environment for EIA purposes akin to that found in the loadline rules, together with rationalisation of the increasing number of special areas in existence or proposed for this purpose. EIA will have to become an integral part of the overall management system in the shipping industry.     

Usefulness of classification and index properties of clay-rich sediments in evaluating sea-bed environmental conditions

A comprehensive study of undisturbed, mostly silty clay samples, taken from large-diameter surface cores collected in the North Atlantic and its bordering seas, shows that measurement of the Atterberg limits, water content, specific gravity of grains and grain-size distribution can provide the basis for predicting many seabed geotechnical and geophysical properties which can lead to a quick assessment of environmental conditions. Thus, the sediment compression curve can be reconstructed, acoustic properties assessed, electrical and thermal resistivities deduced and an indication of the shearing forces, which have affected the sediment, inferred.     

PCDD/F and PCB in harbour seals (Phoca vitulina) from British Columbia: response to exposure to pulp mill effluents

Blubber of harbour seals (Phoca vitulina) sampled from the Strait of Georgia, BC, in 1991 and 1992 contained higher concentrations of polychlorinated dibenzo-p-dioxins and furans (PCDD/F) than did samples from Quatsino Sound on western Vancouver Island. The higher proportions of 1,2,3,6,7,8-hexachlorodibenzodioxin and 2,3,7,8-tetrachlorodibenzofuran in the Strait of Georgia samples probably reflect contamination arising from the discharge of effluents from bleached kraft mills. Higher concentrations of non-ortho- and mono-ortho substituted polychlorinated biphenyls were also found in the Strait of Georgia samples, probably as a result of general industrial activity in the region. Principal components analysis showed that residues were distributed differently between males and females. Within males, concentrations of PCDD, PCDF and PCBs appeared to increase with age. Toxic equivalents (TEQ) to 2,3,7,8-tetrachlorodibenzodioxin in the Quatsino Sd. samples were close to the working guidelines for edible fish used by Health Canada; TEQ calculated for the Strait of Georgia samples exceeded these guidelines by up to a factor of five.